/*****************************************************************************************
 *                                                                                       *
 * OpenSpace                                                                             *
 *                                                                                       *
 * Copyright (c) 2014-2019                                                               *
 *                                                                                       *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this  *
 * software and associated documentation files (the "Software"), to deal in the Software *
 * without restriction, including without limitation the rights to use, copy, modify,    *
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to    *
 * permit persons to whom the Software is furnished to do so, subject to the following   *
 * conditions:                                                                           *
 *                                                                                       *
 * The above copyright notice and this permission notice shall be included in all copies *
 * or substantial portions of the Software.                                              *
 *                                                                                       *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,   *
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A         *
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT    *
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF  *
 * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE  *
 * OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                                         *
 ****************************************************************************************/

#include <modules/galaxy/rendering/renderablegalaxy.h>

#include <modules/galaxy/rendering/galaxyraycaster.h>
#include <modules/volume/rawvolume.h>
#include <modules/volume/rawvolumereader.h>
#include <openspace/engine/globals.h>
#include <openspace/rendering/raycastermanager.h>
#include <openspace/rendering/renderable.h>
#include <openspace/rendering/renderengine.h>
#include <openspace/util/boxgeometry.h>
#include <openspace/util/distanceconstants.h>
#include <openspace/util/updatestructures.h>
#include <ghoul/glm.h>
#include <ghoul/filesystem/filesystem.h>
#include <ghoul/io/texture/texturereader.h>
#include <ghoul/logging/logmanager.h>
#include <ghoul/opengl/ghoul_gl.h>
#include <ghoul/opengl/programobject.h>
#include <ghoul/opengl/texture.h>
#include <ghoul/opengl/textureunit.h>
#include <glm/gtc/matrix_transform.hpp>
#include <fstream>

namespace {
    constexpr const char* GlslRaycastPath =
        "${MODULES}/galaxy/shaders/galaxyraycast.glsl";
    constexpr const char* GlslBoundsVsPath =
        "${MODULES}/galaxy/shaders/raycasterbounds_vs.glsl";
    constexpr const char* GlslBoundsFsPath =
        "${MODULES}/galaxy/shaders/raycasterbounds_fs.glsl";
    constexpr const char* _loggerCat       = "Renderable Galaxy";

    constexpr const std::array<const char*, 4> UniformNamesPoints = {
        "modelMatrix", "cameraViewProjectionMatrix", "eyePosition",
        "opacityCoefficient"
    };
    constexpr const std::array<const char*, 5> UniformNamesBillboards = {
        "modelMatrix", "cameraViewProjectionMatrix",
        "cameraUp", "eyePosition", "psfTexture"
    };

    constexpr openspace::properties::Property::PropertyInfo VolumeRenderingEnabledInfo = {
        "VolumeRenderingEnabled",
        "Volume Rendering",
        "" // @TODO Missing documentation
    };

    constexpr openspace::properties::Property::PropertyInfo StarRenderingEnabledInfo = {
        "StarRenderingEnabled",
        "Star Rendering",
        "" // @TODO Missing documentation
    };

    constexpr openspace::properties::Property::PropertyInfo StepSizeInfo = {
        "StepSize",
        "Step Size",
        "" // @TODO Missing documentation
    };

    constexpr openspace::properties::Property::PropertyInfo AbsorptionMultiplyInfo = {
        "AbsorptionMultiply",
        "Absorption Multiplier",
        "" // @TODO Missing documentation
    };

    constexpr openspace::properties::Property::PropertyInfo EmissionMultiplyInfo = {
        "EmissionMultiply",
        "Emission Multiplier",
        "" // @TODO Missing documentation
    };

    constexpr openspace::properties::Property::PropertyInfo TranslationInfo = {
        "Translation",
        "Translation",
        "" // @TODO Missing documentation
    };

    constexpr openspace::properties::Property::PropertyInfo RotationInfo = {
        "Rotation",
        "Euler rotation",
        "" // @TODO Missing documentation
    };

    constexpr openspace::properties::Property::PropertyInfo StarRenderingMethodInfo = {
        "StarRenderingMethod",
        "Star Rendering Method",
        "This value determines which rendering method is used for visualization of the "
        "stars."
    };

    constexpr openspace::properties::Property::PropertyInfo EnabledPointsRatioInfo = {
        "EnabledPointsRatio",
        "Enabled points",
        "" // @TODO Missing documentation
    };

    constexpr openspace::properties::Property::PropertyInfo DownscaleVolumeRenderingInfo = {
        "Downscale",
        "Downscale Factor Volume Rendering",
        "This value set the downscaling factor"
        " when rendering the current volume."
    };

    constexpr openspace::properties::Property::PropertyInfo NumberOfRayCastingStepsInfo = {
        "Steps",
        "Number of RayCasting Steps",
        "This value set the number of integration steps during the raycasting procedure."
    };
} // namespace

namespace openspace {

    RenderableGalaxy::RenderableGalaxy(const ghoul::Dictionary& dictionary)
    : Renderable(dictionary)
    , _volumeRenderingEnabled(VolumeRenderingEnabledInfo, true)
    , _starRenderingEnabled(StarRenderingEnabledInfo, true)
    , _stepSize(StepSizeInfo, 0.01f, 0.0005f, 0.05f, 0.001f)
    , _absorptionMultiply(AbsorptionMultiplyInfo, 40.f, 0.0f, 200.0f)
    , _emissionMultiply(EmissionMultiplyInfo, 200.f, 0.0f, 1000.0f)
    , _starRenderingMethod(
        StarRenderingMethodInfo,
        properties::OptionProperty::DisplayType::Dropdown
    )
    , _enabledPointsRatio(EnabledPointsRatioInfo, 0.5f, 0.01f, 1.0f)
    , _translation(TranslationInfo, glm::vec3(0.f), glm::vec3(0.f), glm::vec3(1.f))
    , _rotation(RotationInfo, glm::vec3(0.f), glm::vec3(0.f), glm::vec3(6.28f))
    , _downScaleVolumeRendering(DownscaleVolumeRenderingInfo, 1.f, 0.1f, 1.f)
    , _numberOfRayCastingSteps(NumberOfRayCastingStepsInfo, 1000.f, 1.f, 1000.f)
{
    dictionary.getValue("VolumeRenderingEnabled", _volumeRenderingEnabled);
    dictionary.getValue("StarRenderingEnabled", _starRenderingEnabled);
    dictionary.getValue("StepSize", _stepSize);
    dictionary.getValue("AbsorptionMultiply", _absorptionMultiply);
    dictionary.getValue("EmissionMultiply", _emissionMultiply);
    dictionary.getValue("StarRenderingMethod", _starRenderingMethod);
    dictionary.getValue("EnabledPointsRatio", _enabledPointsRatio);
    dictionary.getValue("Translation", _translation);
    dictionary.getValue("Rotation", _rotation);

    if (dictionary.hasKeyAndValue<bool>(VolumeRenderingEnabledInfo.identifier)) {
        _volumeRenderingEnabled = dictionary.value<bool>(
            VolumeRenderingEnabledInfo.identifier
            );
    }

    if (dictionary.hasKeyAndValue<bool>(StarRenderingEnabledInfo.identifier)) {
        _starRenderingEnabled = static_cast<bool>(StarRenderingEnabledInfo.identifier);
    }

    if (dictionary.hasKeyAndValue<double>(StepSizeInfo.identifier)) {
        _stepSize = static_cast<float>(dictionary.value<double>(StepSizeInfo.identifier));
    }

    if (dictionary.hasKeyAndValue<double>(AbsorptionMultiplyInfo.identifier)) {
        _absorptionMultiply = static_cast<float>(
            dictionary.value<double>(AbsorptionMultiplyInfo.identifier)
        );
    }

    if (dictionary.hasKeyAndValue<double>(EmissionMultiplyInfo.identifier)) {
        _emissionMultiply = static_cast<float>(
            dictionary.value<double>(EmissionMultiplyInfo.identifier)
        );
    }

    _starRenderingMethod.addOptions({
        { 0, "Points" },
        { 1, "Billboards" }
    });
    if (dictionary.hasKey(StarRenderingMethodInfo.identifier)) {
        const std::string starRenderingMethod = dictionary.value<std::string>(
            StarRenderingMethodInfo.identifier
        );
        if (starRenderingMethod == "Points") {
            _starRenderingMethod = 0;
        }
        else if (starRenderingMethod == "Billboards") {
            _starRenderingMethod = 1;
        }
    }

    if (dictionary.hasKeyAndValue<glm::vec3>(TranslationInfo.identifier)) {
        _translation = dictionary.value<glm::vec3>(TranslationInfo.identifier);
    }

    if (dictionary.hasKeyAndValue<glm::vec3>(RotationInfo.identifier)) {
        _rotation = dictionary.value<glm::vec3>(RotationInfo.identifier);
    }

    if (!dictionary.hasKeyAndValue<ghoul::Dictionary>("Volume")) {
        LERROR("No volume dictionary specified.");
    }

    ghoul::Dictionary volumeDictionary = dictionary.value<ghoul::Dictionary>("Volume");

    std::string volumeFilename;
    if (volumeDictionary.getValue("Filename", volumeFilename)) {
        _volumeFilename = absPath(volumeFilename);
    }
    else {
        LERROR("No volume filename specified.");
    }
    glm::vec3 volumeDimensions;
    if (volumeDictionary.getValue("Dimensions", volumeDimensions)) {
        _volumeDimensions = static_cast<glm::ivec3>(volumeDimensions);
    }
    else {
        LERROR("No volume dimensions specified.");
    }
    glm::vec3 volumeSize;
    if (volumeDictionary.getValue("Size", volumeSize)) {
        _volumeSize = volumeSize;
    }
    else {
        LERROR("No volume dimensions specified.");
    }

    if (volumeDictionary.hasKey(NumberOfRayCastingStepsInfo.identifier)) {
        _numberOfRayCastingSteps = static_cast<int>(
            volumeDictionary.value<float>(NumberOfRayCastingStepsInfo.identifier)
        );
    }
    else {
        LINFO("Number of raycasting steps not specified for Milkway Galaxy."
              " Using default value.");
    }

    _downScaleVolumeRendering.setVisibility(
        openspace::properties::Property::Visibility::Developer
    );
    if (volumeDictionary.hasKey(DownscaleVolumeRenderingInfo.identifier)) {
        _downScaleVolumeRendering = 
                   volumeDictionary.value<float>(DownscaleVolumeRenderingInfo.identifier);
    }

    if (!dictionary.hasKeyAndValue<ghoul::Dictionary>("Points")) {
        LERROR("No points dictionary specified.");
    }

    ghoul::Dictionary pointsDictionary = dictionary.value<ghoul::Dictionary>("Points");
    std::string pointsFilename;
    if (pointsDictionary.getValue("Filename", pointsFilename)) {
        _pointsFilename = absPath(pointsFilename);
    }
    else {
        LERROR("No points filename specified.");
    }

    if (pointsDictionary.hasKeyAndValue<double>(EnabledPointsRatioInfo.identifier)) {
        _enabledPointsRatio = static_cast<float>(
            pointsDictionary.value<double>(EnabledPointsRatioInfo.identifier)
            );
    }

    std::string pointSpreadFunctionTexturePath;
    if (pointsDictionary.getValue("Texture", pointSpreadFunctionTexturePath)) {
        _pointSpreadFunctionTexturePath = absPath(pointSpreadFunctionTexturePath);
        _pointSpreadFunctionFile = std::make_unique<ghoul::filesystem::File>(
            _pointSpreadFunctionTexturePath
        );
    }
    else {
        LERROR("No points filename specified.");
    }
}

void RenderableGalaxy::initializeGL() {
    // Aspect is currently hardcoded to cubic voxels.
    _aspect = static_cast<glm::vec3>(_volumeDimensions);
    _aspect /= std::max(std::max(_aspect.x, _aspect.y), _aspect.z);

    volume::RawVolumeReader<glm::tvec4<GLubyte>> reader(
        _volumeFilename,
        _volumeDimensions
    );
    _volume = reader.read();

    _texture = std::make_unique<ghoul::opengl::Texture>(
        _volumeDimensions,
        ghoul::opengl::Texture::Format::RGBA,
        GL_RGBA,
        GL_UNSIGNED_BYTE,
        ghoul::opengl::Texture::FilterMode::Linear,
        ghoul::opengl::Texture::WrappingMode::ClampToEdge);

    _texture->setPixelData(reinterpret_cast<char*>(
        _volume->data()),
        ghoul::opengl::Texture::TakeOwnership::No
    );

    _texture->setDimensions(_volume->dimensions());
    _texture->uploadTexture();

    _raycaster = std::make_unique<GalaxyRaycaster>(*_texture);
    _raycaster->initialize();

    global::raycasterManager.attachRaycaster(*_raycaster);

    auto onChange = [&](bool enabled) {
        if (enabled) {
            global::raycasterManager.attachRaycaster(*_raycaster);
        }
        else {
            global::raycasterManager.detachRaycaster(*_raycaster);
        }
    };

    onEnabledChange(onChange);

    addProperty(_volumeRenderingEnabled);
    addProperty(_starRenderingEnabled);
    addProperty(_stepSize);
    addProperty(_absorptionMultiply);
    addProperty(_emissionMultiply);
    addProperty(_starRenderingMethod);
    addProperty(_enabledPointsRatio);
    addProperty(_translation);
    addProperty(_rotation);
    addProperty(_downScaleVolumeRendering);
    addProperty(_numberOfRayCastingSteps);

    // initialize points.
    if (!_pointsFilename.empty()) {
        _pointsProgram = global::renderEngine.buildRenderProgram(
            "Galaxy points",
            absPath("${MODULE_GALAXY}/shaders/points_vs.glsl"),
            absPath("${MODULE_GALAXY}/shaders/points_fs.glsl")
        );
        _billboardsProgram = global::renderEngine.buildRenderProgram(
            "Galaxy billboard",
            absPath("${MODULE_GALAXY}/shaders/billboard_vs.glsl"),
            absPath("${MODULE_GALAXY}/shaders/billboard_fs.glsl"),
            absPath("${MODULE_GALAXY}/shaders/billboard_ge.glsl")
        );

        if (!_pointSpreadFunctionTexturePath.empty()) {
            _pointSpreadFunctionTexture = ghoul::io::TextureReader::ref().loadTexture(
                absPath(_pointSpreadFunctionTexturePath)
            );

            if (_pointSpreadFunctionTexture) {
                LDEBUG(fmt::format(
                    "Loaded texture from '{}'",
                    absPath(_pointSpreadFunctionTexturePath)
                ));
                _pointSpreadFunctionTexture->uploadTexture();
            }
            _pointSpreadFunctionTexture->setFilter(
                ghoul::opengl::Texture::FilterMode::AnisotropicMipMap
            );

            _pointSpreadFunctionFile = std::make_unique<ghoul::filesystem::File>(
                _pointSpreadFunctionTexturePath
                );
        }

        ghoul::opengl::updateUniformLocations(
            *_pointsProgram,
            _uniformCachePoints,
            UniformNamesPoints
        );
        ghoul::opengl::updateUniformLocations(
            *_billboardsProgram,
            _uniformCacheBillboards,
            UniformNamesBillboards
        );

        _pointsProgram->setIgnoreUniformLocationError(
            ghoul::opengl::ProgramObject::IgnoreError::Yes
        );

        GLint positionAttrib = _pointsProgram->attributeLocation("in_position");
        GLint colorAttrib = _pointsProgram->attributeLocation("in_color");

        std::ifstream pointFile(_pointsFilename, std::ios::in);

        std::vector<glm::vec3> pointPositions;
        std::vector<glm::vec3> pointColors;
        int64_t nPoints;

        // Read header for OFF (Object File Format)
        std::string line;
        std::getline(pointFile, line);

        // Read point count
        std::getline(pointFile, line);
        std::istringstream iss(line);
        iss >> nPoints;

        // Prepare point reading
        _nPoints = static_cast<size_t>(nPoints);  
        float maxdist = 0;

        // Read points
        float x, y, z, r, g, b, a;
        for (size_t i = 0;
             i < static_cast<size_t>(_nPoints * _enabledPointsRatio.maxValue()) + 1;
             ++i)
        {
            std::getline(pointFile, line);
            std::istringstream issp(line);
            issp >> x >> y >> z >> r >> g >> b >> a;

            //Convert klioparsec to meters
            glm::vec3 position = glm::vec3(x, y, z);
            position *= (openspace::distanceconstants::Parsec * 100);

            maxdist = std::max(maxdist, glm::length(position));

            pointPositions.emplace_back(position);
            pointColors.emplace_back(r, g, b);
        }

        pointFile.close();

        std::cout << maxdist << std::endl;

        glGenVertexArrays(1, &_pointsVao);
        glGenBuffers(1, &_positionVbo);
        glGenBuffers(1, &_colorVbo);

        glBindVertexArray(_pointsVao);
        glBindBuffer(GL_ARRAY_BUFFER, _positionVbo);
        glBufferData(GL_ARRAY_BUFFER,
            pointPositions.size() * sizeof(glm::vec3),
            pointPositions.data(),
            GL_STATIC_DRAW
        );

        glBindBuffer(GL_ARRAY_BUFFER, _colorVbo);
        glBufferData(GL_ARRAY_BUFFER,
            pointColors.size() * sizeof(glm::vec3),
            pointColors.data(),
            GL_STATIC_DRAW
        );

        glBindBuffer(GL_ARRAY_BUFFER, _positionVbo);
        glEnableVertexAttribArray(positionAttrib);
        glVertexAttribPointer(positionAttrib, 3, GL_FLOAT, GL_FALSE, 0, nullptr);

        glBindBuffer(GL_ARRAY_BUFFER, _colorVbo);
        glEnableVertexAttribArray(colorAttrib);
        glVertexAttribPointer(colorAttrib, 3, GL_FLOAT, GL_FALSE, 0, nullptr);

        glBindBuffer(GL_ARRAY_BUFFER, 0);
        glBindVertexArray(0);
    }
}

void RenderableGalaxy::deinitializeGL() {
    if (_raycaster) {
        global::raycasterManager.detachRaycaster(*_raycaster);
        _raycaster = nullptr;
    }
}

bool RenderableGalaxy::isReady() const {
    return true;
}

void RenderableGalaxy::update(const UpdateData& data) {
    if (_raycaster) {
        //glm::mat4 transform = glm::translate(, static_cast<glm::vec3>(_translation));
        const glm::vec3 eulerRotation = static_cast<glm::vec3>(_rotation);
        glm::mat4 transform = glm::rotate(
            glm::mat4(1.0),
            eulerRotation.x,
            glm::vec3(1, 0, 0)
        );
        transform = glm::rotate(transform, eulerRotation.y, glm::vec3(0, 1, 0));
        transform = glm::rotate(transform, eulerRotation.z,  glm::vec3(0, 0, 1));

        glm::mat4 volumeTransform = glm::scale(transform, _volumeSize);
        _pointTransform = transform;
        //_pointTransform = glm::scale(transform, _pointScaling);

        const glm::vec4 translation = glm::vec4(_translation.value()*_volumeSize, 0.0);

        // Todo: handle floating point overflow, to actually support translation.

        volumeTransform[3] += translation;
        _pointTransform[3] += translation;

        _raycaster->setDownscaleRender(_downScaleVolumeRendering);
        _raycaster->setMaxSteps(_numberOfRayCastingSteps);
        _raycaster->setStepSize(_stepSize);
        _raycaster->setAspect(_aspect);
        _raycaster->setModelTransform(volumeTransform);
        _raycaster->setAbsorptionMultiplier(_absorptionMultiply);
        _raycaster->setEmissionMultiplier(_emissionMultiply);
        _raycaster->setTime(data.time.j2000Seconds());
    }
}

void RenderableGalaxy::render(const RenderData& data, RendererTasks& tasks) {
    // Render the volume
    if (_raycaster && _volumeRenderingEnabled) {
        RaycasterTask task{ _raycaster.get(), data };

        const glm::vec3 position = data.camera.positionVec3();
        const float length = safeLength(position);
        const glm::vec3 galaxySize = _volumeSize;

        const float maxDim = std::max(std::max(galaxySize.x, galaxySize.y), galaxySize.z);

        const float lowerRampStart = maxDim * 0.01f;
        const float lowerRampEnd = maxDim * 0.1f;

        const float upperRampStart = maxDim * 2.f;
        const float upperRampEnd = maxDim * 10.f;

        float opacityCoefficient = 1.f;
        if (length < lowerRampStart) {
            opacityCoefficient = 0.f; // camera really close
        } else if (length < lowerRampEnd) {
            opacityCoefficient = (length - lowerRampStart) /
                                 (lowerRampEnd - lowerRampStart);
        } else if (length < upperRampStart) {
            opacityCoefficient = 1.f; // sweet spot (max)
        } else if (length < upperRampEnd) {
            opacityCoefficient = 1.f - (length - upperRampStart) /
                                 (upperRampEnd - upperRampStart); //fade out
        } else {
            opacityCoefficient = 0;
        }

        _opacityCoefficient = opacityCoefficient;
        ghoul_assert(
            _opacityCoefficient >= 0.f && _opacityCoefficient <= 1.f,
            "Opacity coefficient was not between 0 and 1"
        );
        if (opacityCoefficient > 0) {
            _raycaster->setOpacityCoefficient(_opacityCoefficient);
            tasks.raycasterTasks.push_back(task);
        }
    }

    // Render the stars
    if (_starRenderingEnabled && _opacityCoefficient > 0.f) {
        if (_starRenderingMethod == 1) {
            renderBillboards(data);
        }
        else {
            renderPoints(data);
        }
    }
}

void RenderableGalaxy::renderPoints(const RenderData& data) {
    if (_pointsProgram) {
        // Saving current OpenGL state
        GLenum blendEquationRGB;
        GLenum blendEquationAlpha;
        GLenum blendDestAlpha;
        GLenum blendDestRGB;
        GLenum blendSrcAlpha;
        GLenum blendSrcRGB;
        GLboolean depthMask;

        glGetIntegerv(GL_BLEND_EQUATION_RGB, &blendEquationRGB);
        glGetIntegerv(GL_BLEND_EQUATION_ALPHA, &blendEquationAlpha);
        glGetIntegerv(GL_BLEND_DST_ALPHA, &blendDestAlpha);
        glGetIntegerv(GL_BLEND_DST_RGB, &blendDestRGB);
        glGetIntegerv(GL_BLEND_SRC_ALPHA, &blendSrcAlpha);
        glGetIntegerv(GL_BLEND_SRC_RGB, &blendSrcRGB);

        glGetBooleanv(GL_DEPTH_WRITEMASK, &depthMask);

        glBlendFunc(GL_SRC_ALPHA, GL_ONE);
        glDepthMask(false);
        glDisable(GL_DEPTH_TEST);

        _pointsProgram->activate();

        glm::dmat4 rotMatrix = glm::rotate(
            glm::dmat4(1.0),
            glm::pi<double>(),
            glm::dvec3(1.0, 0.0, 0.0)) *
                glm::rotate(glm::dmat4(1.0), 3.1248, glm::dvec3(0.0, 1.0, 0.0)) * 
                glm::rotate(glm::dmat4(1.0), 4.45741, glm::dvec3(0.0, 0.0, 1.0)
        );

        glm::dmat4 modelMatrix =
            glm::translate(glm::dmat4(1.0), data.modelTransform.translation) *
            glm::dmat4(data.modelTransform.rotation) * rotMatrix *
            glm::dmat4(glm::scale(glm::dmat4(1.0), glm::dvec3(data.modelTransform.scale)));

        glm::dmat4 projectionMatrix = glm::dmat4(data.camera.projectionMatrix());

        glm::dmat4 cameraViewProjectionMatrix = projectionMatrix *
            data.camera.combinedViewMatrix();

        _pointsProgram->setUniform(_uniformCachePoints.modelMatrix, modelMatrix);
        _pointsProgram->setUniform(
            _uniformCachePoints.cameraViewProjectionMatrix,
            cameraViewProjectionMatrix
        );

        glm::dvec3 eyePosition = glm::dvec3(
            glm::inverse(data.camera.combinedViewMatrix()) *
            glm::dvec4(0.0, 0.0, 0.0, 1.0)
        );
        _pointsProgram->setUniform(_uniformCachePoints.eyePosition, eyePosition);
        _pointsProgram->setUniform(
            _uniformCachePoints.opacityCoefficient,
            _opacityCoefficient
        );

        glBindVertexArray(_pointsVao);
        glDrawArrays(GL_POINTS, 0, static_cast<GLsizei>(_nPoints * _enabledPointsRatio));

        glBindVertexArray(0);

        _pointsProgram->deactivate();

        glEnable(GL_DEPTH_TEST);
        glDepthMask(true);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

        // Restores OpenGL blending state
        glBlendEquationSeparate(blendEquationRGB, blendEquationAlpha);
        glBlendFuncSeparate(blendSrcRGB, blendDestRGB, blendSrcAlpha, blendDestAlpha);
        glDepthMask(depthMask);
    }
}

void RenderableGalaxy::renderBillboards(const RenderData& data) {
    if (_billboardsProgram) {
        // Saving current OpenGL state
        GLenum blendEquationRGB;
        GLenum blendEquationAlpha;
        GLenum blendDestAlpha;
        GLenum blendDestRGB;
        GLenum blendSrcAlpha;
        GLenum blendSrcRGB;
        GLboolean depthMask;

        glGetIntegerv(GL_BLEND_EQUATION_RGB, &blendEquationRGB);
        glGetIntegerv(GL_BLEND_EQUATION_ALPHA, &blendEquationAlpha);
        glGetIntegerv(GL_BLEND_DST_ALPHA, &blendDestAlpha);
        glGetIntegerv(GL_BLEND_DST_RGB, &blendDestRGB);
        glGetIntegerv(GL_BLEND_SRC_ALPHA, &blendSrcAlpha);
        glGetIntegerv(GL_BLEND_SRC_RGB, &blendSrcRGB);

        glGetBooleanv(GL_DEPTH_WRITEMASK, &depthMask);

        glBlendFunc(GL_SRC_ALPHA, GL_ONE);
        glDepthMask(false);
        glDisable(GL_DEPTH_TEST);

        _billboardsProgram->activate();

        glm::dmat4 rotMatrix = glm::rotate(
            glm::dmat4(1.0),
            glm::pi<double>(),
            glm::dvec3(1.0, 0.0, 0.0)) *
                glm::rotate(glm::dmat4(1.0), 3.1248, glm::dvec3(0.0, 1.0, 0.0)) * 
                glm::rotate(glm::dmat4(1.0), 4.45741, glm::dvec3(0.0, 0.0, 1.0)
        );

        glm::dmat4 modelMatrix =
            glm::translate(glm::dmat4(1.0), data.modelTransform.translation) *
            glm::dmat4(data.modelTransform.rotation) * rotMatrix *
            glm::dmat4(glm::scale(glm::dmat4(1.0), glm::dvec3(data.modelTransform.scale)));

        glm::dmat4 projectionMatrix = glm::dmat4(data.camera.projectionMatrix());

        glm::dmat4 cameraViewProjectionMatrix = projectionMatrix *
            data.camera.combinedViewMatrix();

        _billboardsProgram->setUniform(_uniformCacheBillboards.modelMatrix, modelMatrix);
        _billboardsProgram->setUniform(
            _uniformCacheBillboards.cameraViewProjectionMatrix,
            cameraViewProjectionMatrix
        );

        glm::dvec3 eyePosition = glm::dvec3(
            glm::inverse(data.camera.combinedViewMatrix()) *
            glm::dvec4(0.0, 0.0, 0.0, 1.0)
        );
        _billboardsProgram->setUniform(_uniformCacheBillboards.eyePosition, eyePosition);

        glm::dvec3 cameraUp = data.camera.lookUpVectorWorldSpace();
        _billboardsProgram->setUniform(_uniformCacheBillboards.cameraUp, cameraUp);

        ghoul::opengl::TextureUnit psfUnit;
        psfUnit.activate();
        _pointSpreadFunctionTexture->bind();
        _billboardsProgram->setUniform(_uniformCacheBillboards.psfTexture, psfUnit);

        glBindVertexArray(_pointsVao);
        glDrawArrays(GL_POINTS, 0, static_cast<GLsizei>(_nPoints * _enabledPointsRatio));

        glBindVertexArray(0);

        _billboardsProgram->deactivate();

        glEnable(GL_DEPTH_TEST);
        glDepthMask(true);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

        // Restores OpenGL blending state
        glBlendEquationSeparate(blendEquationRGB, blendEquationAlpha);
        glBlendFuncSeparate(blendSrcRGB, blendDestRGB, blendSrcAlpha, blendDestAlpha);
        glDepthMask(depthMask);
    }
}

float RenderableGalaxy::safeLength(const glm::vec3& vector) const {
    const float maxComponent = std::max(
        std::max(std::abs(vector.x), std::abs(vector.y)), std::abs(vector.z)
    );
    return glm::length(vector / maxComponent) * maxComponent;
}

} // namespace openspace